Mast "pumping" (not under sail, at the dock).. ?

chrisncate · #1 03-29-2012

So here we are, living on the boat now - not sailing her yet as I have to replace some old standing rigging - but I notice that in wind (like this morning for example), the mast seems to shake and pump quite a bit around the spreaders. It's kind of disturbing while sleeping in the V berth, you can really feel it and hear it. It always "sort" of did this, but we never slept up front until now (it never had cushions and was always storage) - so maybe I am just noticing it more/differently now by sleeping under the mast.

The mast was down for the refit, and put back up with the old rigging (by me, an amateur and not a rigger). I'm not sure how to resolve this, or if it is even a problem for the fairly short term until I can rebuild the rigging. Should I tighten up on the lowers? Any way to eyeball by feel how much tension to apply to the lowers/uppers/front/back wires? I don't have a tension gauge and can't currently buy one...

Help? Do I even heed help or is this alright?

Captainmeme · #2 03-29-2012

I've always wondered about this term "mast pumping". To me it conveys the action of vertical displacement. Yes, that the mast moves up then down. Is that what your mast is doing? Moving up and down? Not side to side or forward and backwards?

Faster · #3 03-29-2012

Some rigs do tend to 'pump' in certain breezes, it can vary with wind strength and wind angle. For example on a previous boat even properly tuned, 20 knots across the beam at the dock resulted in some pumping. It was rarely an issue because we generally wouldn't be on board overnight in those conditions. It never really happened on the hook unless it was really blustery.

You could try tuning the lowers to try to minimize it, esp if you put a little prebend (forward lowers pulling the mast forward slightly) or perhaps just up the tension a bit to see if it helps.

OTOH when that occurs it's kind of like a built-in anchor watch alarm.. go to sleep in calm conditions, the noise will wake you up to have a look around..

casey1999 · #4 03-29-2012

Chris,
Here is a good tuning guide:
selden mast tuning guide - Bing

I also need to replace my standing rigging in the next couple years. How do you plan to change out your forestay, backstay and upper shrouds? Will you rig a temp halyard while you do the work to support? I am a little nervous to be at the top of mast with only a halyard holding her up. Boat looks great.

BubbleheadMd · #5 03-29-2012

CnC-

I just dealt with this issue on my boat, (discussed on another forum). You and I both have "telephone pole" rigs. Thick masts that are only made to have a tiny amount of pre-bend.

Snug up your forward lowers 1/2 turn each. Maybe 1 turn. If the aft lowers get tight when you do this, then loosen them a corresponding amount of turns.

Also, take your jib halyard over to a stbd stanchion base (just pick one) and mark exactly where it reaches the toe rail with a piece of tape. Take the halyard over to the same stanchion base on the port side. The halyard should reach the toe rail at the taped mark on the halyard. If it doesn't, then your mast is canted in one direction or the other, and you need to loosen everything and start over.

Get the mast centered directly over the boat.

Squidd · #6 03-29-2012

Quote:

Also, take your jib halyard over to a stbd stanchion base (just pick one) and mark exactly where it reaches the toe rail with a piece of tape. Take the halyard over to the same stanchion base on the port side. The halyard should reach the toe rail at the taped mark on the halyard. If it doesn't, then your mast is canted in one direction or the other, and you need to loosen everything and start over.

Thats assuming your halyard sheaves are centered at the top of the mast...won't work if they are side by side...

JimMcGee · #7 03-29-2012

Chris,
I get the same thing at the dock when the wind is piping up on the beam. Tuning the rig helped quite a bit, and for my rig the standard tune calls for a bit of additional tension on the foward lowers as Bubblehead suggested. But this didn't eliminate the problem completely.

I found posts on some forums that suggested taking a couple of wraps around the mast with your main halyard to break up the wind currents. That didn't help with my boat (though it might with yours).

A Loos gauge isn't terribly expensive, I think around $60 at Defender, and makes tuning the rig easy. The cheaper solution is a big box of foam earplugs -- $15 from Lowes.

Don't laugh my wife always wears them when sleeping aboard.

You get used to the sounds your boat makes and you register a lot of information about her without realizing it just by how she sounds and feels.

The noise that woke me bolt upright out of a sound sleep was the sound of claws dragging across the deck right over my head in the v-berth.

Turned out it was a heron!

JimMcGee · #8 03-29-2012

You may have already covered this in another post.

How are your cruising plans coming? You must be pretty close to casting off?

Brent Swain · #9 03-29-2012

Running back stays, from the spreaders to a point well aft ,eliminate the problem.

chrisncate · #10 03-29-2012

Quote:

Originally Posted by casey1999

Chris,
Here is a good tuning guide:
selden mast tuning guide - Bing

I also need to replace my standing rigging in the next couple years. How do you plan to change out your forestay, backstay and upper shrouds? Will you rig a temp halyard while you do the work to support? I am a little nervous to be at the top of mast with only a halyard holding her up. Boat looks great.

I will do the halyard thing, I have a chair as well as mast steps so I will strap the chair on my butt and climb on up and secure myself once up top. I too get nervous up there, but I have been up my steps enough to be fairly comfortable with it now. I still don't like it, but I think it'll be alright as long as the halyard is clipped good.

Thanks for the boat compliment